Field of the Invention
Example embodiments relate to a pressure swing adsorption (PSA) system and process designed for recovering and concentrating the heavier species from a feed gas stream also containing lighter species, or recovering and concentrating the lighter species from a feed gas stream also containing heavier species, or recovering and concentrating both the heavier and lighter species from a feed gas stream containing such heavier and lighter species. More specifically, example embodiments relate to systems and methods for enhanced separation of lighter from heavier species.
Description of Prior Art
A PSA process is generally used for the purification and recovery of a light gas species from a gas mixture wherein the rest of the gas species have either a stronger thermodynamic affinity or faster adsorption kinetics with the adsorbent or layers of adsorbents being utilized in the process. In these processes the light product stream containing the lighter species leaves the beds at the same pressure of the feed stream, while the rejected heavy product stream leaves the beds at the lowest pressure of the PSA cycle. Examples of processes utilized in this way are the purification of hydrogen from reforming gas, the concentration of oxygen from air, the concentration and purification of methane from nitrogen, and the purification of ethanol from water at elevated temperatures.
Less commonly, PSA is also used for the concentration and recovery of a heavy gas species from a gas stream wherein the rest of the species have either less thermodynamic affinity or slower adsorption kinetics with the adsorbent or layers of adsorbents being utilized in the process. In these processes the heavy product stream containing the heavy species leaves the beds at the lowest pressure of the PSA cycle while the rejected light product stream leaves the beds at the same pressure of the feed stream. Examples of processes utilized in this way are the separation of carbon dioxide from flue gas, the removal of carbon dioxide from the tail gas of a PSA process for hydrogen purification, the purification of oxygen from a stream containing nitrogen and oxygen impurities, the purification of nitrogen from air, and the purification of methane from a stream containing nitrogen as impurity.